Indicia readers fall into two main classes depending on the method used to capture barcodes. Area-image scanners (i.e., imaging scanners) use digital imaging technology to acquire images that are processed and analyzed to decode indicia (e.g., barcodes). Illumination requirements and complicated electronics limit this class of indicia readers.
Single-line laser scanners (i.e., laser scanners) scan barcodes with a collimated beam of light. As the light is swept across a barcode, the reflected light is modulated with the barcode's information. This reflected light can be decoded and the encoded data can be output to a host device. These scanners can be small, robust, and inexpensive. In addition, these scanners are especially useful for long-range scan applications.
The scan element is the mechanism used to sweep the laser beam. Various types of scan elements have been devised. Continued development in this area is driven by a need to optimize scan stability, precision, and reliability. Simple laser scanner designs that minimize cost and complexity are generally preferred, therefore minimizing the complexity of the scan element, while maintaining overall scanner performance, is important.
An oscillating scan mechanism is a scan mechanism in which a light source (e.g., laser or LED) is deflected (i.e., scanned) by a reciprocating mirror. The reciprocating motion is achieved by a force interaction between a permanent magnet and a nearby coil (i.e., a solenoid). When the coil is driven with an alternating electric current, the scan element oscillates back and forth. There are different types of scan elements, and the type of scan element used in a scanner depends on the application.
Shaft based scan elements use a mirror and a magnet attached to a rotational body. The rotational body can rotate about a fixed shaft or can be rigidly mounted to a rotatable shaft. Both configurations allow the mirror and magnet to rotate about the shaft axis.
Cantilever-hinge scan elements use a flexible material to form a hinge. This flexible hinge is affixed to one side of a mirror/magnet assembly. The other side of the hinge is attached to a fixed frame. Scanning consists of the oscillating motion enabled by a flexible hinge.
Torsional scan elements use a mirror and magnet mounted directly or indirectly to a shaft made from a flexible material. The shaft is generally affixed along the center axis of the mirror and magnet. The shaft may be twisted to allow the mirror and magnet to oscillate.
Nonlinear elastomeric materials can be used to form a torsional scan element (i.e., flexible scan element). This material is flexible, durable, and stable. The material may be molded to form a flexible scan element with various features. The molding process simplifies construction and reduces cost. The flexible properties of this material, however, may hinder performance when the flexible scan element is mechanically shocked (e.g., impact).
Shock causes excessive motion that could damage the flexible scan element or negatively affect the scanner's performance. Flexible scan elements can be protected from shock through external components that limit excessive scan element motion. These external components, however, must provide clearance to avoid interference with the moving parts involved with scanning motion.
A need, therefore, exists for a flexible scan element without excessive motion resulting from shock or impact and without the risk of unwanted contact between moving and fixed components.